1. Field of the Invention
The present invention relates to a fuel pump and a method of manufacturing the fuel pump.
2. Description of the Related Art
Recently, an electromagnetic fuel pump for vehicles which is composed of a motor section and pump section is widely used. In general, such a fuel pump is designed to discharge a fixed quantity of fuel more than the quantity required by an engine. Reduction in the electric power consumed by the fuel pump is effective to suppress fuel consumption, and reduction in electric load of an alternator is an important subject of conserving limited resources and protecting the global environment.
Because the motor section and the pump section are composed of various parts and components having variety in sizes and performance, the fuel pump must be designed to discharge a quantity of fuel required for the engine taking such variation into account. As a result, such a pump is apt to discharge more quantity of fuel than required by the engine, thereby wasting electric power. In a fuel pump system which has a fuel-return passage, as the returned fuel quantity increases temperature of the fuel in the fuel tank rises, thereby generating fuel vapor.
JPU-3-129793 proposes a fuel pump which has a magnetic movable member disposed inside the yoke between adjacent permanent magnets. Such a movable member is moved from the outside by an adjusting screw to change the magnetic resistance between two permanent magnets, thereby changing the rotation speed of the motor and the resultant fuel quantity.
However, such a conventional fuel pump needs an additional member for sealing the movable member and the adjusting screw connected to the movable member, resulting in increase in production steps and cost.